Blow hammer



Feb. 17

R. MEYER 31.0w HAMMER 2 Sheets-Sheet 1 filed May 31, 1968 INVENTORRUDOLF MEYER I ATTORNEYS Feb. 11,1970 MEYER 3,495,666

' 31.0w; HAMMER. Q Filed May 31, 1968 2 Sheets-Sheet 2 INVENTOR RUDOLFMEYER BY 1 6M; 9 $4M ATTORNEYS United States Patent 3,495,666 BLOWHAMMER Rudolf Meyer, im Berg 8, Ennetbaden, Switzerland Filed May 31,1968, Ser. No. 743,575 Int. Cl. B2511 11/04, 17/24 U.S. Cl. 173119 12Claims ABSTRACT OF THE DISCLOSURE The present invention relates to animpact hammer, and more particularly to an impact hammer with aperiodically actuated impact piston.

As high as possible an impact frequency is desirable with impacthammers. The prior art impact pistons driven either directly by a motor,by way of a connecting rod or by means of compressed air, do not permitin principle an increase in the impact frequency by reason of theinertia effect and of the elasticity of the actuating or drivingcompressed air. Furthermore, crank drives for the production of theimpact movement have as a con sequence vibrational forces by reason ofthe eccentric masses which are effective not only in the impactdirection but also transversely with respect thereto which is verytroublesome, disagreeable and fatiguing. They have their origin in thetransverse components of the movement of the connecting rods. Theaccelerating and decelerating forces which occur thereby and which acthorizontally cannot be compensated by simple means.

The present invention starts with the concept to limit movements to thelongitudinal axis. In order to obtain simultaneously a strong impactaction, the driving force does not act directly on the impact piston butat first on a spring which stores the impact energy, and which springonly accelerates the impact piston to its velocity required for theimpact movement.

The present invention is concerned with an impact hammer having animpact piston periodically moved in the longitudinal axis under theeffect of a spring. The drive takes place by a rotary motor.

The present invention essentially consists in that the impact piston isprovided in its axial direction with a drive rod and a spring isarranged concentrically thereto pressing against the impact piston, andin that rollers arranged on both sides and symmetrically to the driverod within roller bearings abut under pressure, whereby at least one ofthe rollers serves as driving roller, and this driving roller isprovided over a part of its circumference with a friction surface withthe shape of a body of rotation, and thus this frictional surface withinits range is in frictional connection with the drive shaft, and therebythe other roller serves as counter-pressure roller, and in that theremaining part of the circumference of the driving roller has a smallerradius and is not in frictional connection within the area of thesmaller radius with the drive shaft so that with a rotating driveroller, the impact piston is raised by the mutual frictional forcewithin the circumferential area of the frictional connection and thespring is stressed thereby, and whereupon within the area in which nofrictional connection 3,495,666 Patented Feb. 17, 1970 ice exists, theimpact piston snaps back under the effect of the spring and carries outits impact work.

Accordingly, it is an object of the present invention to provide animpact hammer which is simple in construction, yet avoids theaforementioned shortcomings and drawbacks encountered in the prior art.

Another object of the present invention resides in an impact hammer witha periodically displaced impact piston that permits an increase in theimpact frequency.

A further object of the present invention resides in an impact hammer ofthe type described above which minimizes vibrational forces andtherewith minimizes compensating means.

These and further objects, features, and advantages of the presentinvention will become more obvious from the following description whentaken in connection with the accompanying drawing, which shows, forpurposes of illustration only, two embodiments in accordance with thepresent invention, and wherein:

FIGURE 1 is a cross-sectional view through an impact hammer inaccordance with the present invention showing the arrangement inprinciple thereof;

FIGURE 2 is a cross-sectional view through a modified embodiment of animpact hammer in accordance with the present invention, representing animproved arrangement; and

FIGURE 3 is a cross-sectional view, taken along line A-A of FIGURE 2.

Referring now to the drawing wherein like reference numerals are usedthroughout the various views to designate like parts, and moreparticularly to FIGURE 1, reference numeral 1 designates therein thehousing which comprises the drive mechanism. A guide cylinder 2 isconnected to the housing 1. The displaceable impact piston 3 togetherwith its impact surface 3a is disposed within the guide cylinder 2,axially guided along the interior walls thereof. The impact piston 3carries out the periodic impacts against the impact tool 4 displaceablyarranged axially below the impact surface 3a. The work tool may be, forexample, a chisel that has a collar 4a. The collar 4a is so guidedwithin the walls 2:: that it can carry out periodically and freely inthe downward direction its impact force corresponding to the impactmovement with a relatively short working path. The impact body is underthe counter-pressure of the storage spring 4 which rests against thehousing 1. The return movement of the chisel after each impact takesplace under the counter-pressure of the spring 12 and is limited by thewall 2a.

The piston 3 is provided in its axial direction with a drive rod orshaft 6. The force storage spring 5 is arranged concentrically theretoand presses against the impact piston 3. Rollers 7 and 8 are present atthe housing 1 and are arranged in ball bearings on both sides of thedrive shaft '6, as indicated, for example, by reference numeral 19 inFIGURE 2. In the illustrated position, the rollers 7 and 8 abut underpressure against the drive shaft 6. One roller 7 is provided inconnection therewith over a part of its circumference with a cylindricalsurface as friction surface 7a in the shape of a body of rotation. Theroller 7 presses against the drive shaft 6 over the circumferential areaof 7a whereas the roller 8, disposed opposite to roller 7 symmetricallyand axially parallelly, presses against the drive roller 7 ascounter-pressure roller. The axes of the rollers 7 and 8 are disposedparallel in a plane perpendicular to the drive shaft 6.. The frictionsurface 7a is thereby in frictional connection with the drive shaft 6over a partial area of the circumference thereof. The remaining partialarea 7b of the circumference of the roller 7 has a somewhat smallerradius. The transition takes place at the leading edge 7c. The latter isslightly a rounded off in order to avoid an excessively abrupttransition.

Outside of the area of the surface 7a, a small gap thus exists betweenthe drive shaft 6 and the drive roller 7. No frictional connectionexists between the drive roller 7 and the drive shaft 6 within that partof the circumference. The roller 7 is simultaneously driving roller andis driven in a conventional manner by a motor by way of a geartransmission (not shown).

The operation is as follows:

When the motor has driven the driving roller 7 in the direction of thearrow, the friction surface 701 comes in pressure contact at its leadingedge 7c with the friction surface of the drive shaft 6. As a result ofthe frictional force transmission resulting thereby, the drive rod 6 isseized during the further operation under clamping pressure and isthereby forcibly displaced upwardly together with the impact piston. Thefriction slippage still relatively large in the first stroke range,especially within the rounded-off area of the edge 7c, decreases veryrapidly; the sliding friction passes over into a static friction oradhering friction that no longer slips. The drive rod 6 together withthe impact body is torn along with great acceleration upwardly untilafter passage of the entire friction surface 7a, the latter again comesout of contact with the drive rod 6. Simultaneously, the spring iscompressed and thus the subsequent impact work stored until thefrictional force transmission stops after passage of the frictionsurface. The movement of the impact body now reverses freely under theimpact of the spring force, and the impact body is displaced downwardlywith a large accelerational force by the spring 5 and strikes the chisel4. During the further rotation of the now freely rotating drive roller7, the leading edge 70 again reaches into pressure contact of the driverod 6. The operation repeats itself. The counter-pressure roller 8thereby carries out a corresponding rotation.

The arrangement according to FIGURE 1 offers the advantage of greatsimplicity. However, its output is limited. The latter can be increasedin that the counter-pressure roller is also constructed as drive roller.For that purpose, the counter-pressure roller is connected with thefirst drive roller so as to rotate symmetrically thereto.

The rotational speed of the drive and therewith the number of impactsper second is limited by the time during which the impact body carriesout its impact freely. The impact movement has to be ended before theleading edge 70 again comes into pressure contact with the frictionsurface. The larger the spring force of the spring, the smaller theimpact time and the greater the impact frequency. The friction slippageis connected with an energy loss during the gliding friction. It can bekept small in that a small slippage path is achieved by a large abutmentpressure of the driving roller.

FIGURES 2 and 3 illustrate such an arrangement which is more capable ofgreater outputs. In these two figures, reference numeral 1 againdesignates the housing having an installed driving motor 12 and atranismission 13. The guide cylinder 14 is arranged at the housing 1.The axially displaccable impact piston 3 is disposed within the housing1 which carries out its impact movements by way of an intermediate pieceon the work tool 16, for example, a chisel, arranged therebelow andaxially guided.

The drive rod 9 is provided with two mutually opposite parallel frictionsurfaces 9a and 9b. Driving rollers 17 and 18 are arranged on both sidesand symmetrically with respect to the drive shaft 9 in roller bearings19. The driving rollers 17 and 18 are coupled to each other rotationallysymmetrically by way of gears 15 and 16. The driving rollers 17 and 18are provided over a part of the circumference thereof with frictionsurfaces 17a and 18a disposed rotationally symmetrically to each other.The friction surfaces 17a and 18a are in frictional connection underhigh radial pressure with the parallel, mutually opposii? frictionsurfaces 9a and 9b of the drive shaft 9.

The ball bearings disposed also symmetrically to the drive shaft 9 areradially so adjustable by any conventional means that the drive rollerspress against the drive shaft 6 with the requisite friction pressurethereof. The friction surfaces are cylinder surfaces of equal radius;they extend with the same angle of rotation rotationally symmetricallyto each other. Within the area of the remaining angle of rotation thedrive rollers 17 and 18 have a somewhat smaller radius so that a gapresults between the same and the drive shaft in which no frictionalcontact can occur. The leading edges 17c and are rounded off in order toavoid an excessively abrupt entrainment of the drive shaft from thestandstill. The pressure spring 5 is installed into the guide cylinder14 which presses axially against the impact body. The impact bodystrikes at first against the sealing displaceably intermediate piece 20only by means of which the impact takes place on the Work tool 4. Theone drive roller 17 is connected by way of the transmission gear 13 withthe electric motor 12 built into the housing 1. With the arrangementaccording to FIGURES 2 and 3, the lifting of the drive rod takes placeby way of two symmetrical and axially parallel cylindrical frictionsurfaces by means of two driving rollers which are driven rotationallysymmetrically. The best possible force transmission on the impact pistonresults therefrom. The impact piston 3 is provided with channels 3bdisposed at its circumference by way of which a pressure equalizationtakes place between the upper and lower spaces of the guide cylinder.

While I have shown and described only two embodiments in accordance withthe present invention, it is understood that the same is not limitedthereto but is susceptible of numerous changes and modifications asknown to a person skilled in the art. For example. the drive shaftinstead of prismatic form with fiat friction surfaces may also beconstructed of cylindrical form. The driving rollers receivecorresponding friction surfaces with cylindrical recesses.

Instead of the spring 5, an elastically effective air cushion may alsobe utilized whereby corresponding seals are necessary at the housingwith respect to the drive shaft and the impact piston 3. The channels31: then are obviated.

Thus, it is obvious that the present invention is not limited to thedetails shown and described herein, and I therefore do not wish to belimited thereto but intend to cover all such changes and modificationsas are encompassed by the scope of the appended claims.

I claim:

1. An impact hammer and the like having an impact piston periodicallymovable in the direction of its longitudinal axis under the effect ofspring means, and rotary motor means for driving said impact piston,wherein the improvement comprises a drive rod connected with the impactpiston substantially in its axial direction, said spring means beingdisposed about said drive rod and normally resting on said impactpiston, and roller means abutting against the drive rod under pressureon oth sides thereof and at least approximately symmetrically thereto,one of said roller means forming a drive roller and being provided Overa part of its circumference with a surface in the shape of a body ofrotation, said surface being in frictional connection with the drive rodwithin its circumferential area so that with a rotating drive roller theimpact piston is raised by the mutual frictional forces within thecircumferential area of the friction connection and the spring means isstressed thereby whereupon the piston snaps back under the effect of thespring means within the area in which no frictional connection existsbetween the driving roller and the drive rod and carries out its impactwork.

2. An impact hammer according to claim 1, further comprising ballbearing means for rotationally supporting said roller means on bothsides of the drive shaft.

3. An impact hammer according to claim 2, wherein the other roller meansis also constructed as a drive roller and serves as counter pressureroller, and means operatively connecting said two roller means with saidrotary motor means to rotate symmetrical to said one r ller means.

4. An impact hammer according to claim 3, wherein said drive rod has theshape of a cylinder.

5. An impact hammer according to claim 3, wherein said drive rod has theshape of a prism.

6. An impact hammer according to claim 1, wherein the other roller meansis also constructed as a drive roller and serves as counter pressureroller, and means operatively connecting said two roller means with saidrotary motor means to rotate symmetrical to said one roller means.

7. An impact hammer according to claim 1, wherein said spring means is acompression spring.

8. An impact hammer according to claim 1, wherein said spring means isan air cushion adapted to be compressed.

9. An impact hammerand the like having an impact piston periodicallymovable in the direction of its longitudinal axis, comprising a driverod operatively connected with the impact piston and disposedsubstantially in its axial direction, and means for imparting impactmovement to said piston including elastic energy storage means stressedby movement of said piston in a direction opposite its impact direction,roller means abutting under pressure against the drive rod and disposedon both sides thereof at least approximately symmetrically thereto, atleast one of said roller means forming a drive roller and being providedover a part of its circumference with a friction surface the shape of abody of rotation, said friction surface being in frictional connectionwith the drive rod within the circumferential area thereof, and drivemeans for at least said one roller means so that with a rotating driveroller means the impact piston is displaced by the frictional forces inthe direction opposite the impact direction and the elastic means isstressed whereupon the piston snaps back under the effect of the elasticmeans within the circumferential area of the one roller means in whichno frictional connection exists between the driving roller means and thedrive rod.

10. An impact hammer according to claim 9, further comprising means foradjustably supporting at least said one roller means to adjust thecontact pressure.

11. An impact hammer according to claim 9, wherein the two roller meansare constructed as drive rollers, the other roller means serving ascounter-pressure roller, and means operatively connecting said tworoller means with said rotary motor means to rotate symmetrical to saidone roller means.

.12. An impact hammer according to claim 11, further comprisingadjustable bearing means for adjustably supporting said two roller meansto adjust the abutment pressure thereof with said drive rod.

References Cited UNITED STATES PATENTS 2,317,158 4/1943 Westover 173-1192,342,601 2/1944 Pyle 173-119 3,053,100 9/1962 Luhm l73119 JAMES A.LEPPINK, Primary Examiner

